Variable resistance assembly



May 27, 1958 G. J. MUCHER VARIABLE RESISTANCE ASSEMBLY Filed Sept. 16,1955 INVENTOR figg?? Jm'zef ATTORNEYS United States Patent O VARIABLERESISTANCE ASSEMBLY George J. Mueller, Rochester, N. H., assignortoClarostat Mfg. Co., Inc., Dover, N. H., a corporation of New YorkApplication September 16, 1955, Serial No. 534,834

4 Claims. (Cl. 20L-48) This invention relates to a structurally andfunctionally improved electrical control embodying a detent structurewhich in its functionings will not interfere with or interrupt theelectrical circuit within which the control is included.

As is well appreciated, in connection with controls of the variableresistance and potentiometer types, it is frequently desirable toincorporate a structure such that the operator-without visualinspection-will be instantly able to determine the relative positions ofthe control elements. Especially in installations for use by the ArmedForces, this determination should be capable of achievement by the senseof touch and despite the fact that the operator may be wearing gloves.

Therefore, it is a primary object of the invention to furnish animproved control in which the relative positions of the shiftable partswith respect to other portions of the assembly may be determined by feeland in which the operator will not interrupt or otherwise inter fetewith an established circuit in properly determining this position.

Other. objects are those of providing a structure which will embrace asimple design and be capable of manufacture by quantity productionmethods at minimum expense, aside from the fact that the design willresultV in a mechanism capable of being operated through a great numberof cycles without any failure occurring on the part of the control.

With these and other objects in mind, reference is had to the attachedsheet of drawings illustrating one practical embodiment of theinvention, and in which:

Fig. 1 is a rear view of a control;

Fig. 2 is a transverse sectional view taken along the line 2 2 in thedirection of the arrows as indicated in Fig. l;

Fig. 3 is a view similar to Fig. 1, but showing the parts adjusted to adifferent position;

Fig. 4 is a transverse sectional view taken along the line 4--4 in thedirection of the arrows as indicated in Fig. 3;

Fig. 5 is a face view of the control with the rotor removed; and

Fig. 6 is a perspective view of the contact element which forms a partof the control.

In these views, the numeral 10 indicates the body of the control, which,in accordance with conventional design, is preferably annular and formedof an insulating material. It mounts a resistance which may take theform of a strip of dielectric material around which closely spaced wirewindings 11 are disposed; the resistance being set within an arcuategroove formedin body 10. As shown especially in Figs. 2 and 4, one edgeof that resistance is thus exposed beyond the face of the casing ormounting body. The ends of the resistance are connected to terminals 12conveniently projecting beyond the control and to whichcurrent-conducting leads (not shown) are connected.

The resistance is concentrically disposed with respect i assetatiPatented May 27, 1958 ICS to and spaced from a contact ring 13. Aterminal 14 may be integral with this ring and extend through a notch inbody 10 at a point intermediate terminals 12. Terminal 14 is likewiseconnected to a current-conducting lead. Resilient bearing portions 15extend inwardly from the ring and engage with the surface of a recess 16formed in body 1G so as to maintain the ring in proper position.

With a View to providing a contact which bridges the gap betweenresistance 11 and ring 13 and traverses these elements, a rotor isfurnished. As shown, this may include a substantially semi circular disc17 of insulating material provided with a preferably noncircular openingthrough which the similarly contoured and reduced end 18 of shaft 19projects. The latter is rotatably supported in bushing 20 atxed to body10. Retaining plates 21 and 22 may overlie and underlie the body 17 andbe provided with openings through which the reduced end 13 of the shaftextends. The end of that shaft may be headed after the parts are securedto it so that the disc portion 17 will rotate with the shaft. The latteris prevented from moving in an axial direction outwardly by, forexample, a plate 23 which is attached to the shaft and bears against theinner surface of bushing assembly 20. This plate may also act as a stopby engaging a projecting portion of body 10. Inward axial movement ofthe shaft with respect to the remaining control parts is convenientlyprevented by a C-ring 24 riding within a groove formed in the shaft andbearing against the outer edge of the bushing 20.

Secured to the inner face of disc 17 by, for example,

rivets 2S is a mounting ring 26. This attachment may continue throughoutan area of around lOO". A greater or lesser area of attachment mayobviously be resorted to. In any event, a substantial portion of ring 26(preferably in excess of extends beyond disc or plate 17 andconveniently includes bowed portions 27 between which a pair ofoutwardly extending parts 2S are provided. Between these, the materialof the ring is reduced to furnish a bridging portion 29. The latter maybe rounded in cross-section and extend in an inward direction so thatthe bridging portion acts as a fulcrum for a contact element. ThatContact element has been illustrated to best advantage in Fig. 6.

l As therein shown, it may include a generally blockshaped body 29formed of a copper graphite compound or any other suitable conductingmaterial and having a length in excess of the distance between ring 13and resistance 11. Its width should be such that it can be accommodatedbetween the projecting portions 28 of the rotor ring 26. lt is formed inits underface with a transverse notch or recess 3@ of roundedconfiguration and corresponding in outline to the bridging portion 29. Atransversely curved contact face 31 extending substantially parallel toaxis of block 29, is included in the surface opposite that within whichnotch 3@ is formed. An inclined and similarly rounded contact face 32forms a continuation of and merges into face 31. if desired, a shallowgroove 33 may also be included in the block and adjacent to notch orrecess 39. Thus, a member is furnished which, as shown especially inFigs. 2 and 3,

is resiliently supported by those parts 27 of ring 26` which extendbeyond plate or disc 17. Therefore,

surfaces 31 and 32 of the block will ride in firm contact with ring 13and resistance 11. Also, the block will be capable of rocking around thefulcrum provided by the bridging strip 29 while lateral movements of theblock will be confined by the projecting portions 28. Obviously,therefore, with a turning of shaft 19, the block may be caused totraverse the entire operative area of the resistance strip 11 and tovary the eiectrical values established by the control of which it formsa part.

asesee Now, with a view to providing an operator-perceptible assemblywhich will enable the user to determine the position of the contact withrespect to the resistance by feeL a detent structure is furnished. Witha view to simplifying the present illustration, only a single detent hasbeen shown. That detent has been illustrated as occupying a positionadjacent one end of the resistance 11. It will be obvious that while inmany respects this is a preferred structure, any suitable number ofdetents could be embodied and they might variously be positionedaccording to the needs of a given circuit. As illustrated, the detentwill include an inwardly extending portion 34 preferably integral withring 13. The surface of this extension will be bulged upwardly tofurnish a rib 3S. of travel of the contact block 29. Therefore, intraversing this Zone of the ring, the block will pass over the rib 35.

Assuming therefore that the parts are assembled in the manner shown inFigs. l and 2, an operator may rotate shaft 19 to cause the contact totraverse the resistance and contact ring and thus vary the values withinan electrical circuit. Any inequalities or unevenness of the parts willhave no effect on this operation in that the block Z9 will simplyfulcrum around the strip 29 as it rides over any uneven portions. At thesame time, incident to the resiliency embodied in ring 2.6, especiallyadjacent the bridging strip 29, a firm and even electrical contact willprevail during this traversal. The same operation of the parts willoccur when the contact passes over the detent provided by rib 35. Inthat case, surface 32 riding in contact with the ring 13 will simply camover the rib. In such camming, it will rock around strip 29 as shownespecially in Fig. 4. So moving, its surface 31 will remain inengagement with the resistance Accordingly, no interruption will occurto the electrical circuit which is involved. However, the operator willbe entirely cognizant that the contact is traversing the detentstructure in that he will feel the increased resistance to turningoffered by the shaft 19 as the contact cams over the detent.

Thus, among others, the several objects of the invention as specificallyaforenoted are achieved. Obviously numerous changes in construction andrearrangements of the parts might be resorted to without departing fromthe spirit of the invention as defined by the claims.

I claim:

l. ln a variable resistance assembly in combination rThat rib willextend within the path a body, a resistance element mounted by said bodyfor traversal by a contact, a contact ring concentrically disposed withrespect to said resistance and mounted by said body, a rotor movablyconnected to said body, a contact connected to said rotor and bridgingsaid ring and said resistance for traversal thereof, means between saidcontact and contact ring providing, upon said rotor being turned, anoperator-perceptible impediment to rotor movement and means forming partof the connection between said rotor and said contact whereby the latterremains in electrical association with said resistance over the entireoperative length thereof.

2. In a variable resistance assembly as in claim l, said means betweensaid contact and contact ring comprising a protrusion on said ring inthe path to be traversed by said contact and said contact beingrockingly mounted to oscillate as it engages said protrusion.

3. In a variable resistance assembly as in claim 1, said means formingpart of the connection between said rotor and said contact including afulcrum part rockingly engaging said contact for enabling said contactto remainv in electrical association with said resistance over theentire traversal. path thereof.

4. Ina variable resistance assembly in combination a body, a resistanceelement mounted by said body for traversal by a contact, a contact ringconcentrically disposed with respect to said resistance and mounted bysaid body, said contact ring being provided with a surface for traversalby a contact and having a detent intersecting a zone of said surface, arotor movably connected to said body, said rotor including a ring-shapedelement being provided with a bridging strip, a contact formed with anotch for rockingly engaging said bridging strip, said contact bridgingsaid ring and resistance for .simultaneous traversal thereof, wherebysaid detent imposes an operator-perceptible impediment to traversal ofsaid ring and said resistance by said contact as said rocking engagementbetween said element and said contact retains said contact in electricalassociation with said resistance.

. References Cited in the le of this patent UNITED STATES PATENTS

